In electronic circuits, power on reset (POR) is an electronic device incorporated into an integrated circuit (IC) which is operable to detect power applied to the IC and generate a reset pulse through the entire circuit to enable the IC to attain a known state. A simple POR circuit can be composed of an RC device that charges as the supply voltage rises. A device such as a Schmitt trigger can be used so that the rising charged voltage of the RC network generates a pulse based on the two threshold voltages of the Schmitt trigger. When the input voltage at the Schmitt trigger from the RC network reaches the first threshold voltage the output signal generated by the Schmitt trigger switches to generate a first edge of the POR signal. Charging of the RC network is intended to have sufficient duration that the POR can reset all internal circuits before charging voltage reaches the second threshold voltage of the Schmitt trigger to deactivate.
The power on reset pulse is used to initialize sequential logic circuits upon power-up. If the sequential logic powers up in the wrong state, catastrophic system malfunction can result.